The German Federal Agency for Nature Conservation (BfN) is working with a consortium of offshore wind companies to find ways to reduce the noise created during construction of wind farms.  An article in Der Spiegel is a good introduction to the efforts:

“From the standpoint of environmental protection, it’s necessary to decrease noise pollution in marine ecosystems,” BfN acknowledges in the introduction of its recent report. The study looks to the guidelines set forth by the Federal Environment Agency (UBA), which suggest that noise outside of a 750 meter radius from the construction site should not exceed 160 decibels. Techniques like bubble curtains, according to the BfN report, can meet this standard.However Greenpeace takes issue with this value because it is based on single-sound exposure — and it takes much more than a single punch into the bed rock of the sea floor to install a wind turbine foundation.

Eight companies are working together to investigate noise-reduction techniques; this article summarizes their goals.  This “Permanent Joint Working Group” is co-hosting a conference in September along with German federal agencies; here’s a brief intro, and here’s the conference website (good luck with your online translation service!)